This is a National Stage Application of PCT/JP99/07333 filed on Dec. 27, 1999, now WO 00/50495 published on Aug. 31, 2000, which claims priority to Japanese Applications 042868/99, filed on Mar. 22, 1999 and 276327/99, filed on Sep. 29, 1999.
The present invention relates to a prepreg comprising a liquid rubber composition impregnated into a reinforcing fiber by heat, pressure and the like, and relates to a fiber-reinforced rubber material comprising the prepreg, the liquid rubber contained in the prepreg being crosslinked by heat or the like.
The present invention also relates to a fiber-reinforced rubber material of which substrate containing rubber component is reinforced by core material composed of prepreg of which reinforcing fiber is impregnated with rubber component. Moreover, the present invention relates to tires, hoses, and transmission belts used in automobiles and office automation equipment which use these fiber-reinforced rubber materials.
Fiber-reinforced rubber materials reinforced by reinforcing fibers have been widely used in industrial products, such as tires, belts, and hoses. These rubber products undergo repeated deformation and particularly require resistance to fatigue from flexing.
Carbon fibers have superior heat resistance and superior water resistance, in addition, to high modulus and high strength. Thus, using thereof as reinforcing fibers, fiber-reinforced rubber materials having significantly high dimensional stability and weather resistance are obtained. Carbon fibers, however, have disadvantages, e.g., poor resistance to fatigue from friction between filaments and poor adhesion to rubber. When a fiber-reinforced rubber material using a carbon fiber undergoes flexing fatigue, filaments break or separation occurs at interfaces between fibers and rubber.
As an attempt to prevent fatigue due to friction between filaments, Japanese Unexamined Patent Application Publication No. 60-85001 discloses a carbon fiber impregnated with a liquid resin or a liquid rubber. In such a method, however, friction between filaments is insufficiently prevented and resistance to fatigue from flexing of the fiber-reinforced rubber material must be further improved.
As attempts to improve adhesion to rubber, Japanese Unexamined Patent Application Publication Nos. 62-149977 and 62-149978 disclose improvements in adhesion of a core material including a carbon fiber bundle: impregnated with liquid butadiene rubber or liquid acrylonitrile-butadiene rubber to solid isoprene as a substrate. In such a method, however, adhesion is not sufficiently improved and resistance to fatigue from flexing of the fiber-reinforced rubber material must be further improved.
No practical carbon fiber-reinforced rubber material which exhibits sufficient heat resistance, water resistance, and dimensional stability due to properties of the carbon fibers and which exhibits resistance to fatigue from flexing has been found.
In order to solve the above-mentioned problems, the present invention includes the following constitution. That is, a prepreg comprising a liquid rubber composition having a viscosity in a range of 0.01 Paxc2x7s to 100 Paxc2x7s at 70xc2x0 C. and containing substantially no solvent, the liquid rubber being impregnated into a reinforcing fiber, and a fiber-reinforced rubber material comprising the prepreg in which the liquid rubber is crosslinked.
In order to solve the above-mentioned problems, the present invention includes the following constitution. That is, a fiber-reinforced rubber material of which substrate comprising a rubber component is reinforced by a core material composed of a prepreg of which reinforcing fiber is impregnated with the same rubber component.